Crystal Phase Engineering of Ultrathin Alloy Nanostructures for Highly Efficient Electroreduction of Nitrate to Ammonia

Abstract

Electrocatalytic nitrate reduction reaction (NO3RR) toward ammonia synthesis is recognized as a sustainable strategy to balance the global nitrogen cycle. However, it still remains a great challenge to achieve highly efficient ammonia production due to the complex proton‐coupled electron transfer process in NO3RR. Here, the controlled synthesis of RuMo alloy nanoflowers (NFs) with unconventional face‐centered cubic (fcc) phase and hexagonal close‐packed/fcc heterophase for highly efficient NO3RR is reported. Significantly, fcc RuMo NFs demonstrate high Faradaic efficiency of 95.2% and a large yield rate of 32.7 mg h−1 mgcat−1 toward ammonia production at 0 and −0.1 V (vs reversible hydrogen electrode), respectively. In situ characterizations and theoretical calculations have unraveled that fcc RuMo NFs possess the highest d‐band center with superior electroactivity, which originates from the strong Ru─Mo interactions and the high intrinsic activity of the unconventional fcc phase. The optimal electronic structures of fcc RuMo NFs supply strong adsorption of key intermediates with suppression of the competitive hydrogen evolution, which further determines the remarkable NO3RR performance. The successful demonstration of high‐performance zinc‐nitrate batteries with fcc RuMo NFs suggests their substantial application potential in electrochemical energy supply systems.

Vacancy-Rich SnO2 Quantum Dot Stabilized by Polyoxomolybdate as Electrocatalyst for Selective NH3 Production

“…With an increase in KNO 3 concentration in the electrolyte, two prominent redox features were visible between −0.15 and −0.55 V (Figure a) while the growth of the predominant catalytic current above −0.55 V was indicative of catalytic reduction of nitrate. According to the literature reports, the first redox wave at 0.06 V can be assigned to nitrate to nitrite while the −0.32 V peak could be attributed to the further reduction of nitrite to ammonia. , A linear correlation of the peak current with the variation of [NO 3 – ] concentration in the electrolyte provided a first-order dependence with respect to the nitrate concentration (Figure b). A cyclic voltammetric (CV) study in variable scan rates and the linear correlation between the cathodic peak current ( i c ) (at −0.32 V vs RHE) versus square root of scan rate (υ 1/2 ) indicates that the eNOR occurs on the electrode surface after diffusion of the nitrate ions from the electrolyte (Figure c and Figure S19).…”

Electronic Structure Design of Transition Metal-Based Catalysts for Electrochemical Carbon Dioxide Reduction

“…Phase engineering of nanomaterials (PEN) has emerged as a powerful strategy for tailoring the characteristics and enhancing the performance of nanocatalysts toward various applications, including the electrochemical CO 2 RR. ,− The unique atomic arrangements in different crystal phases of nanocatalysts result in distinctive electronic structures, influencing their surface activity. ,, It is worth noting that at the nanoscale, phase engineering can be more effectively executed in nanomaterials in contrast to their bulk counterparts, caused by the compelling influence of surface properties. In the realm of CO 2 RR, the phase of catalysts deeply affects the interaction between catalyst surface and adsorbates, indicating further regulation of reaction activity, intermediate selectivity, and long-term stability .…”

Controlled Synthesis of Unconventional Phase Alloy Nanobranches for Highly Selective Electrocatalytic Nitrite Reduction to Ammonia

“…Recently, crystal phase engineering has been emerging as an effective approach to modulate the intrinsic physicochemical properties of metal nanomaterials, and thus improve their catalytic activities. [29][30][31][32][33][34][35][36][37][38] To date, various monometallic nanomaterials with unconventional crystal phases, such as face-centered cubic (fcc)-2H-fcc heterophase gold, [39] fcc ruthenium, [40][41] 2H palladium [42] and hexagonal close-packed (hcp) rhodium, [43] have been obtained and demonstrated much superior catalytic activities over their common phase counterparts in different electrochemical reactions. Note that the catalytic performance of monometallic nanomaterials usually suffers from the limited types of adsorption sites on the surface, which makes it difficult to achieve the concurrent adsorption and stabilization of multiple intermediates in the multistep reactions like NO 2 RR.…”